From my experience, the first test was the most difficult in terms of nerves. I haven't tested in a while, but I was pretty nervous still then. I used to compete in equestrian events (okay, not the same, but you get the gist) and had terrible butterflies before I went into the ring, but they went away as soon as I was on course. Same for testing in aikido; terrible nerves before and then they go away once the test starts. I think that the nerves serve a good purpose in testing. Keep you on your toes.